Function line number pass

Implemented pass which prints the line number and the path to the source
code file where the function is defined.

Usage example:
> opt -load $LLVM_LIB/LLVMFunctionLineNumber.so -disable-output -
function line-number -function-name vpx_mem_set_functions vpxdec.bc

> /home/jan/libvpx/vpx_mem/vpx_mem.c 586